1. Field of the Invention
The present invention relates to an improved electrochemical gas electrode for use in fuel cells wherein electrical energy is produced directly by the oxidation of a fuel, in gas detection cells wherein the electrical energy produced is correlated with the concentration of fuel in a gas mixture and in gas separation cells wherein a component of a gas mixture is electrochemically oxidized and thereby removed from the gas stream.
2. Description of the Prior Art
Fuel, gas detection and gas separation cells generally comprise first and second conductive electrodes separated by an electrolyte, a supply of fuel gas contacting a gas-permeable surface area of the first electrode (the anode), an oxidant supply for cathodically depolarizing the second electrode (the cathode) and means for electrically connecting the electrodes. Electrodes are commonly composed of a precious metal catalyst, a catalyst support material and a hydrophobic coating and bonding material. The precious metal catalyst provides a gas absorption surface at which electrochemical oxidation occurs. The catalyst support material is porous and has a large surface area. The hydrophobic coating and bonding material binds the catalyst to the catalyst support and also controls the flooding of the electrolyte to the gas side of the electrode surface. Such electrodes are expensive and difficult to prepare with the proper balance of porosity, activity and wettability.
U.S. Pat. No. 3,297,487 discloses fuel cells using catalyst-coated electrodes consisting of silicon and vanadium, chromium, molybdenum, tungsten, manganese, iron, cobalt or nickel. The cathode need not be catalyst-coated if the cell is operated above about 65.degree. C. U.S. Pat. No. 3,432,355 discloses fuel cell electrodes having thin film hydrophobic coatings and having a catalyst bonded thereto by means of a polytetrafluoroethylene binder. U.S. Pat. No. 3,622,487 discloses a detector cell which is capable of monitoring oxides of nitrogen in gas streams and which has a precious metal anode and a metal oxide cathode. The gas being analyzed dissolves in a thin film of electrolyte over the anode surfaces but it must be kept from diffusing through the electrolyte to the cathode.